ATLANTA (AP) _ Airlines have grounded several Boeing 757 jets while they scramble to make repairs or find replacement parts because of cracks in the air-flow blades of their Pratt & Whitney engines.
At least two in-flight engine failures have been blamed on the cracks since late last year.
The cracking has happened in the stator vane, a stationary blade made of steel alloy that helps direct air flow through the engine.
The cracking can cause an engine to shut down. But the 757 has two engines and can fly on one.
``We believe the cracking is caused by the variety of pressures the engine is undergoing,'' said Mark Sullivan, a spokesman for Pratt & Whitney.
Pratt & Whitney, based in East Hartford, Conn., is working with airlines to repair or replace the part, which it is redesigning. But the new design will not be tested and certified for use until December.
``We think we should have this problem wrestled to the ground by the end of the year,'' Sullivan said.
Pratt & Whitney supplies its PW2037 and PW2040 models for 757-200s flown by Delta, Northwest, TWA, United and UPS. The Air Force uses the PW2040 on C-17 cargo jets.
Because there have been so many cracks, airlines are having a hard time finding replacement blades.
Atlanta-based Delta has parked planes with engine cracks for which it has been unable to obtain replacement stator vanes, said Kathleen Bergen, a spokeswoman for the FAA's Atlanta regional office.
Delta would not disclose how many planes were grounded, but an airline source who requested anonymity said nine. Delta has 121 757s, the biggest such fleet among U.S. airlines.
TWA has been working feverishly to secure repairs for its 27 757s, which represent 15 percent of its total fleet, said John Hotard, a spokesman for the airline's parent, American Airlines.
United had to ground four of its 98 757s late last year because of stator cracks but has returned the planes to service, spokesman Joe Hopkins said.
The Federal Aviation Administration said it is monitoring the problem but has issued no advisories or orders regarding it.
On March 4, a Delta flight descending into Portland, Ore., had an engine failure because of a crack but landed safely, spokesman Russ Williams said.
In November, a United flight was forced to return to Denver after one of its engines failed because of stator cracks, according to a United report filed with the FAA.
The 757 has gained popularity for its low operating costs and ability to land on short runways and in hot weather. U.S. airlines had 586 757s last year, according to the Air Transport Association.